Free-Form: Key Questions Answered

Everything you want to ask, and everything you need to know

By Karlen McLean, ABOM, NCLC

Here, complete with insider input, are the basics to help you understand, recommend, dispense, and sell free-form created lenses.

HOW FREE-FORM IS DONE

Here's a brief overview of how free-form processing works, with an optically optimized PAL lens design that's surfaced entirely on the back of the lens blank using a free-form generator. According to Darryl Meister, ABOM, Carl Zeiss Vision, Inc.:

1. The order is supplied to the free-form lab. This includes the wearer's Rx requirement, standard fitting measurements, frame dimensions, and position-of-wear measurements.
2. The order information is transmitted by the lab to the proprietary optical design engine server. Optically optimized in real time using patient data, a target design is determined. The ray-traced performance of the initial lens is compared against the target design and is mathematically manipulated until it achieves the desired performance. The newly calculated lens design is then transmitted back as a points file.
3. The points file is transmitted to a computer-numerically-controlled (CNC) free-form generator along with a cutting file containing carefully determined machine instructions for controlling the parameters of the generating process.
4. A puck similar to a semi-finished single vision lens is then subjected to a twostage, single-point cutting process. This begins with a rough cut and concludes with a final finishing pass. In some cases, an additional smoothing cut may be performed between the rough cut and finishing pass.
5. The lens is then dynamically polished using a computer-controlled polishing process with a soft lap tool guided by a polishing file—a third computer file containing machine instructions that control a number of polishing parameters.
6. Finally, the lenses are subjected to any additional treatments, such as hard coating and AR.

SELLING FREE-FORM

WHY FREE-FORM IS IMPORTANT

It's as simple as being able to offer your patients the best vision possible via the latest technology. It can be broken down into three categories for training. If some patients need more particulars, reports Brad Main, FNAO, HOYA Vision Care North America:

OPTIMIZATION: One example is aspheric/atoric design. The design is the same conventional design and blanks that have been in use for some 30 years, but new surface geometry optimizes the optical performance of lenses more efficiently.

CUSTOMIZATION: This includes design adaptations to the Rx and frame dimensions on a case-by-case basis. This is where proprietary, patented technology steps in to create lenses, for example, separating the design into two components (vertical and horizontal optical progression) and then distributing it over the front and back of a lens blank.

PERSONALIZATION: By collecting objective and subjective information—typically with a specialized measuring device—what's discovered is used to create a truly personalized vision experience for each wearer.

WHAT FREE-FORM IS

It's important to remember six key points about free-form created lenses, says Pete Hanlin, ABOC, LDO, Essilor of America, starting with the fact that "digital surfacing is a process for making optical lenses, not a design."

1. The main difference between digital and traditional surfacing is digital surfacing's ability to produce complex surfaces with extreme accuracy. Traditional surfacing can only produce spherical and toric surfaces.
2. Digital surfacing can be used to create simple single vision or very complex progressive surfaces. The ability of a lens to provide visual comfort and performance is determined by the quality of the design, not the process used to produce it.
3. Digital surfacing is variously referred to as direct-to-surface, CNC, and free-form. All refer to basically the same process.
4. The most significant variable involves the process used to calculate the design. Digital surfacing processes require significantly more calibration and control compared to traditional surfacing.
5. There are two inherent benefits common to nearly all digitally surfaced PALs: reduction of marginal astigmatism and reduction of "rounding errors." That is, since any power can be produced, digitally surfaced lenses are theoretically accurate to within 0.01 diopters.
6. Remember: all lenses that bend light will have aberrations, and spherical surfaces create aberration. It's a matter of how those aberrations are managed that provides a unique benefit to each wearer.

LABS AND FREE-FORM

Free-form production can be a boon and a bust for wholesale labs.

On the upside, there's seemingly no end to the designs that can be fabricated, which means there's a customized lens solution for all your patients. "We're utilizing free-form production in all facets of our operations," observes Steve Seibert, president of Three Rivers Optical in Pittsburgh, Pa. "Some examples are dual-side PAL designs, our private label backside PAL, specialty PAL designs, and special orders including lens designs that may be off the market now but that patients still want. Additionally, we're creating pristine lens surfaces for top-end ARs."

Another advantage is that, in most cases, turnaround is faster. "It allows us to start wrap orders the same day they're received," says Glenn Hollingsworth, general manager of Robertson Optical of Atlanta. "Proprietary software decenters the design in the blank, eliminating many cut-out issues in large frames."

Free-form is, however, a monetary leap for labs. "There aren't too many labs that can and will invest three to four million in on-block manufacturing (OBM)," says Greg Rudin, president of Expert Optics in Shorewood, Ill., about Expert's recently installed, virtually hands-free system. "You can't make 2010 lenses on 1999 equipment. The open platform means the ability to offer all designs independently."

How do you know your lab's capabilities and updates besides just making a phone call to ask? Rudin advises that you tour your lab every 18 months or so to see what's new, and to tour another lab for comparison. "If there's a better product out there, as a consumer, I want to know about it," he says. "Eyewear and automobiles are a lot alike to consumers: both are expensive and they want to know what their purchase will bring them."

Where are labs intending to go with freeform technology? As far as they can…and in many cases that means all the way.

Looking ahead, John Haskins, president of Slabs Plus in Ruskin, Fla., concludes: "Every lab will need to ramp up as the momentum for free-form lenses continues to grow through technology, advertising, and education." EB